While high speed sheet feeders have been utilized for many years, their designs have relied generally upon prior knowledge of the exact thickness in size of sheets to be fed. In this manner, the operating parameters of the feeder could be precisely adjusted to account for a particular sheet thickness.
Sheet feeding is a complex process that involves singulation of the downstream most sheet in a stack so that it is no longer frictionally bound to more upstream sheets in the stack. This sheet is then fed at an appropriate time down a feeding path to a location at which it can be utilized. At some point, the stack must be advanced so the next sheet in the stack is brought into position for singulation.
Since the process of feeding involves many variables, there are many points at which failure (e.g. jamming or double feeding of sheets) can occur. Hence, the friction of the singulator, at a degree to which a sheet is singulated away from other sheets in the stack, the exact amount that the stack is advanced and the angle at which the sheet is driven from the stack are carefully controlled. Variations in stack size, thickness and texture of the sheets in the stack can, thus, cause a failure in the feeding process in such prior art devices.
Accordingly, this invention has as one object to provide a high speed sheet feeder that feeds sheets of different thicknesses and textures without need of prior adjustment.
It is another object of this invention to provide a high speed sheet feeder with increased reliability even during high speed operation.
It is yet another object of this invention to provide a high speed sheet feeder that can quickly be adapted to feed sheets either singularly or in an overlapping configuration.
It is yet another object of this invention to provide a high speed sheet feeder that is relatively compact, yet can handle sheets having a variety of sizes.